#include <Eigen/Eigenvalues>
#include <iostream>
using namespace Eigen;
using namespace std;
void main() {
	Matrix3f eimR1; eimR1.setIdentity();
	Quaternionf q1 = Quaternionf(eimR1);
	Quaternionf q2 = q1.conjugate();
	float fAD = q1.angularDistance(q2);
	cout << fAD;
	return;
}
